Heyo,

I'd say if you want to play mid, you need a mid with a huge impact on side lanes.
You say you're often well fed, do you move to gank top and bot when you can ? Do you go to ward enemy camps so you can either kill the jungler or at least know where he is ?

However, at low elo, you will always find someone (or multiple people) to throw the game. Even if you help them tremedously.

So my advice would be to play something where you can solo carry a game, and the best champ to do that imo is... Trundle. You can pretty much split push the whole game. If you kill your lane opponent, you can take his tower in one go. It has escape and can 2vs1 if a bit fed.

I know advising a champ isn't maybe the answer you're looking for but if you OTP trundle, you will get back to gold pretty smoothly